I just noticed that following. I touched one of my pis heatsinks and it was very hot to the touch with the Navio attached. I could not touch it for more than 2 seconds ???. With the navio off the i can keep my finger on the heatsink?
I have noted the RPIO problems and the Barometer problems a couple of times before. The RPIO problem will sometimes dissapear but the barometer problem always exist
Could you please take a photo of a properly screwed Navio 2 and a screenshot of i2cdetect -y 1?
Most of the times issues like yours have been solved by a tighter connection. In case the screws don’t change anything, I might wanna ask you to give a little squeeze on the connector making the connection between the boards rock solid and issue i2cdetect -y 1 one more time.